Pictures: "Supergiant," Shrimp-Like Beasts Found in Deep Sea

More Than a Handful

Marine scientists have hoisted up a mysterious new species of "supergiant" amphipods from one of the deepest ocean trenches in the world, scientists announced Thursday.

Seven of the pinkish, shrimp-like animals crawled into a trap left in the Kermadec Trench, an abysmal rift in the seafloor off the northern coast of New Zealand that sinks down 6.2 miles (10 kilometers).

The largest amphipod measured in at 11 inches long (28 centimeters)—nearly three times larger than the previous record-holder—and was captured at a depth of about 4.35 miles (7 kilometers). It's not yet clear whether the newfound giants represent a new species or just especially big supergiant amphipods.

Alan Jamieson, a marine biologist at the University of Aberdeen and co-leader of the expedition, was hoping to find a species of snailfish that had eluded scientists' capture for half a century—but was shocked by the giant, shrimp-like amphipod instead.

"Amphipods are common to deep-sea trenches, but they're usually 2 to 3 centimeters [about an inch] long. They turn up in a matter of minutes like a swarm of bees and simply devour all of the bait," Jamieson said.

"Now all of the sudden we have this monster amphipod and no other known sizes in between."

Catch of the Day

Members of the marine expedition hold up a few of the supergiant amphipods recovered from the abyss. (From left to right: Toyo Fujii, Alan Jamieson, and Ashley Rowden.)

The team has probed the depths of other deep-sea trenches around the Earth, but only the Kermadec Trench is known to harbor the huge crustaceans.

"We can't think of any one factor that would make these amphipods so much larger than amphipods in other trenches," Jamieson said. "It's a mystery."

Adding to the mystery is the animals' elusiveness.

"The weirdest thing was, on some spare days at the end of expedition, we went back to the same spot but never caught any or saw any on our camera," he said. "We caught seven in eight hours on the first day, then they completely disappeared."

Elusive Snailfish

Photograph courtesy Oceanlab, University of Aberdeen

The supergiant species of amphipods wasn't a wish-list item on the expedition, as no one knew they existed until now.

The marine scientists' top quarry—shown here munching on a decaying mackerel about 4.7 miles (7.5 kilometers) deep in the Kermadec Trench—was a species of snailfish not spotted in the region since the 1950s.

"It doesn't matter which trench you're at in the world, you'll find quite a dense population of snailfish," Jamieson said. "They always find some ecological niche halfway down the walls of a trench and thrive."

Simple Trap for a Supergiant

Photograph courtesy Oceanlab, University of Aberdeen

You can't be too picky about what you haul up from the depths in a trap like this. Once a hunk of bait is inside and it's dropped into the water, it's first come, first served—and amphipods almost always turn out in the largest numbers.

Jamieson and his team are gathering genetic data from amphipods recovered in deep-sea trenches around the world to understand how they're related and how far they can travel. So far, the team's results suggest the creatures—against all odds—can travel thousands of miles to reach another trench.

"There is some kind of gene flow going on, so there must be a mechanism by which they can spread around," Jamieson said.

"It must be [in the] egg phase, where they float then sink back down," he said. "I just can't picture one of these amphipods going from point A to point B any other way. It'd be like a cockroach walking from one end of New Zealand to the other."